The "arrear contribution" refers to an additional current year contribution that is related to a previous tax year in which you did not claim your maximum allowable deduction. This extra contribution of R1 800 can be claimed annually in respect of all previous years in which you did not claim your full 15% (of non-pensionable income) deduction. So if you contributed R9 000 to an retirement annuity last year and you have contributed R18 000, then you can make an additional contribution of R1 800 (over and above your 15% of non-pensionable income) in each of the next five years. However, the contribution limit to all retirement funds together (including retirement annuities) is set to increase to 27 5% of gross income from 1 March 2016 so claiming this is unlikely to offer a major added benefit. The tax saving on R1 800 (a number which has not changed for many years) has lost much of its significance anyway. Over 40 years, you could claim additional contributions of R72 000, for a total tax saving of R29 520. The present value of that at 6% inflation is only around R11 000 (and that's your best outcome). You can go back for as many years as you have contributed to an retirement annuity and provided SARS with the relevant proof in each year. SARS keeps a record of your "excess contributions" (contributions not allowed for tax). It will deduct these from your taxable income in future years to the extent that your future contribution in any tax year falls below the maximum contribution limit for that year (either under the current "15% of non-pensionable income" rule, or under the new "27,5% of taxable income" rule). Any contribution not claimed for tax is returned to you untaxed when you retire (either added to your tax-free cash lump sum, or as untaxed annuity income).